Refugees from Iraq are on the move. More than 1.2 million of them have already fled the country, and recent anecdotal reports—a many-fold increase in the buses traveling daily from Baghdad to Jordan this summer, for example—suggest that the tempo of the exodus is increasing. If the violence in Iraq spreads, the number of Iraqis who flee to neighboring states may well triple. And if the nascent civil war in Iraq unfolds the way most other recent civil wars have, the refugees will remain outside Iraq for years.

All too often, where large numbers of refugees go, instability and war closely follow—as Middle Eastern history attests. Palestinian refugees, who with their descendants number in the millions, have been a source of regional violence and regime change for decades. They helped provoke the 1956 and 1967 Arab-Israeli wars by conducting cross-border attacks against Israel and inviting Israeli retaliation against the Arab states that hosted them. Later they turned against their hosts and catalyzed a civil war in Jordan (1970–71) and in Lebanon (1975–90). The “Palestinian question”—and the paltry Arab-state reaction to it—has also contributed to coups by militant Arab nationalists in Egypt, Iraq, and Syria.

The Palestinian experience in this regard is not unique. The fall of the Zairean ruler Mobutu Sese Seko, for instance, and the subsequent civil war in Zaire, which claimed roughly 4 million lives, can be traced directly to the arrival of Rwandan refugees in 1994. Refugees have a knack for upsetting the status quo.

The iconic image of the refugee is a bedraggled woman clutching her child as she stumbles into a blighted aid camp. But this picture is incomplete. Refugee camps, which are often under international protection but do not have international policing, can become sanctuaries for militia groups. Host governments often find it hard to stop these militias, even when they want to, either because they lack the military strength to do so or because fighters hide among innocent civilians. In fact, militia leaders sometimes become the leaders of the refugee community, offering protection, imposing their will on any rivals, and recruiting new fighters from among the camp’s many traumatized, jobless young men. Tribal elders and other leaders who might oppose violence may find themselves enfeebled by both the trauma of flight and the loss of their traditional basis of power (typically, control of land). As a result, refugee camps can become deeply radicalized communities, dangerous to their host countries in several ways. The mere presence of militias among the refugees tends to embroil the host country in war by making it a target.

Most Iraqi refugees are not in camps, but dispersed among local populations. But refugees, whether in camps or not, can also corrode state power from the inside, fomenting the radicalization of domestic populations and encouraging rebellion against host governments. The burden of caring for hundreds of thousands of refugees is heavy, straining government administrative capacity and possibly eroding public support for regimes shown to be weak, unresponsive, or callous. And the sudden presence of armed fighters with revolutionary aspirations can lead disaffected local clans or co‑ religionists to ally with the refugees against their own government, especially when an influx of one ethnic or religious group upsets a delicate demographic balance, as would likely be the case in some of Iraq’s neighbors.

To date, Jordan and Syria have taken in the vast majority of fleeing Iraqis—in large part because those countries have been the most welcoming. But in the worst-case scenario of an all-out civil war, Iraq’s other neighbors would not find it easy to resist the influx of refugees. This map shows some of the places that might be most affected.

Syria. Refugees pose a tremendous danger to the frail regime of Bashar al-Assad. Already, Syria is dealing with an influx of 450,000 Iraqis, and may bear the brunt of a Sunni exodus from western Iraq. Most Syrians are also Sunni, but the Assad regime is not: it rests on Syria’s Shiite Alawite community, which composes about 12 percent of the population. Many Sunnis see the Alawites as heretics, and from 1976 to 1982 Bashar’s father, Hafez al-Assad, brutally repressed the insurgent Sunni Muslim Brotherhood. Iraqi Sunni Muslims waging a long conflict from Syrian soil could once again radicalize Syria’s own Sunni com-munity. This time it could call on support from outside Syria, and perhaps seek sanctuary in Iraq as well.

Jordan. Some 700,000 Iraqi refugees—many of them Sunnis from Baghdad and western Iraq—have already fled to Jordan. This influx is alarming in a country of just 6 million people, especially one that has experienced rising Islamist militancy in the last decade. The jihadist Abu Musab al-Zarqawi used Iraq as a base to operate against his home country, sending Iraqi terrorists to bomb three hotels in Amman in 2005. Jordan’s security services are highly capable, but large numbers of experienced Sunni insurgents and jihadist recruiters on Jordanian territory would make their job exceptionally difficult.

Saudi Arabia. In an all-out civil war, both Sunni and Shiite refugees could pour back and forth across Saudi Arabia’s long border with Iraq. In addition to using Saudi Arabia as a safe harbor, militants in both groups would likely become involved in Saudi politics. Armed Iraqi Shiites might support recently restive Saudi Shiites—who are concentrated in the oil-rich Eastern Province—by giving them weapons and an operational haven. Likewise, Iraqi Sunni fighters—many of whom see the Al Saud as bigger devils than even George W. Bush—might join with Saudi terrorists who have been openly fighting the regime since 2003, turning the guerilla methods they’ve learned against the Saudi government. The Saudi regime is surprisingly resilient. But at the very least, such problems would push oil prices far higher.

Iran. Iran might look at the arrival of Shiite refugees as an opportunity to extend its influence in Iraq, by supporting and coopting the militants among them. Tehran is already training, funding, and arming various Iraqi Shiite bands, and having a large refugee community on its soil could facilitate its efforts. But the immediate presence of hundreds of thousands of traumatized Shiites could also generate domestic pressure on Tehran to intervene directly in Iraq in order to stop Sunni atrocities against Iraq’s Shiite community.

Kuwait. Because it is an easy drive from southern Iraq, many Iraqi Shiites might flee to Kuwait should the violence in Iraq escalate. About one-third of Kuwait's 1 million citizens are Shiite, and the presence of a few hundred thousand Iraqi Shiites would shift Kuwait's political balance. It could stir the country's Shiites to rise up agains the ruling Sunnis. The Al Sabah have always managed to weather internal unrest, but the scale of such a problem would be far greater than any they've faced before.

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